Electrical Shock While Working On Dryer ?

Hello:
Have the typical Kenmore electric clothes dryer.
While oiling a drum roller underneath, I received a pretty good electrical
shock. Really surprising, as I wasn't touching anything other than the
frame.
Was spraying a bit with WD-40 when it happened. Seemed like such an
innoculous
thing I was doing, I didn't bother unplugging
Wasn't touching any wires or other parts, to the best of my knowledge.
Plenty of room underneath to avoid them.
It was plugged in with the heavy 3 prong 220 plug.
I guess one of these prongs is the Neutral, and the other two are for the
the
two 220 V phases.
Questions:
a. What likely was the reason for the shock ?
Could it be a voltage between the neutral and a real ground (thru me) ?
b. Should I run a wire from the dryer case to a good cold water pipe for
a ground ?
Thanks,
Bob

3 prong 220Volt plugs are dangerous because if an OPEN circuit should
develop in the neutral wire, full voltage can appear on the appliance
case...
YES! I would run a wire from the dreyer case to ground on any 3 prong
220V appliance...
I have done that to mine...
Mark

Depends on what you mean by open circuit. I wouldn't assume that a dryer
that's turned off is consuming _no_ power. It could have electronics that
are always on.
As for full voltage on the case, consider: in a three wire dryer/stove
connection, the two hots are connected to the elements (thru switching) to
provide 240V.
The 120V motor/clock/timer etc. are connected to one hot _and_ the third wire,
and the case is connected to the third wire too.
If you cut the third wire between the dryer and the panel, the case
becomes live if there's anything switched on on the 120V side.
If the dryer is operating at that point, what happens is that the heaters
stays on, yet the timer and motor stop.
Eg: if the motor is switched on, one side is connected to a hot, the other
side is connected to a _floating_ (not grounded) case. If you're grounded
(eg: touching a pipe, or a grounded clothes washer) and touch bare metal
on the case, you get zapped - _thru_ the component that's trying to
conduct power (eg: the motor).
I would think most likely that the OP has a neutral/grounding problem.
It's best to kill power to appliances before opening it, even if you
think it's totally off and figure you can stay away from the hot side
of the switch.
When I had to replace the heating element in our dryer a few days
ago, I killed the breaker. I didn't know for sure whether the element
switching killed _both_ hots or just one, and I didn't want to find
out the hard way. I tested it anyway to make sure I got the right
breaker.
[I didn't want to have to move the dryer out to unplug it.]

--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.

Many 220V appliances have the case "bonded" to the neutral. If the
neutral opens, voltage can appear on the cabinet. I doubt it would be
220V though, more likely 120V through the motor or some other 120V
circuit inside the unit that taps one leg and neutral as it's current
source.
Newer homes are wired with 4 wire 220V outlets to prevent this, that
way both the neutral and ground wires have to open before this could
occur.

It essentially _can't_ be 240V. The only way you can get hit with a 240V
shock is if you touch both legs of the main simultaneously. The highest
voltage (normally! ;-) available in a house is 120V relative to ground.

--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.

...
Actually, I don't think it's true. Neither UL nor CSA have
allowed anything like that for over my 35 year's experience, and
the current rules, including EC definitely do not allow it. An
exposed metal part must be either connected to earth, or "double
insulated" (which does NOT mean two layers of insulation). The
only safety spec number I recall at the moment is the old UL1459
or I could provide more backup. Retired, don't cha know <g>.
Pop

Up until a few years ago, the US NEC permitted stoves and dryers
to be connected using three wire connections. Two hots, and
a third wire that acts as _both_ a neutral (for 120V loads
like clocks and 120V accessory outlets) and for bonding the
frame to ground.
Canadian CEC hasn't permitted this for at least 30 years.
US NEC has changed so that it requires 4 wire circuits just
like Canadian CEC does. The difference being that the NEC
has more "grandfathering" than the CEC does.
In CEC, when you install a new stove or dryer, you must bring
existing circuits up to current spec. In NEC, you only have to bring
existing circuits up to current spec if you're changing the circuit.
You can't buy a 3 wire cordset in Canada (I don't think we _ever_
required 3 wire outlets. It went directly from 4 wire direct
connect to 4 wire outlets). You still can in the US.
Yeah, I think the NEC permissivity was dumb too.

--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.

There is no neutral in a 220 connection. Two hots, no neutral,
and a ground if it is a new enough install.
Yes, I know the really new stuff has a four wire connection that
has 2 hots, ground, and now a neutral in case the modern appliance
needs 110 volts.
I would check the ground circuit and the case ground with regard
to getting shocked. Electricity should not go to the case unless
something is wrong.
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)
snipped-for-privacy@7cox.net

I've never seen one of those. It may be true with some
all-electronic stoves. But certainly not anything with a 120V
accessory outlet.
Transformers, for anything but very tiny loads, would be more
expensive to manufacture than simply providing a fourth wire,
or using devices that don't need 120V.

--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.

Interesting question. You prompted me to do a little test and in my
test WD-40 did not conduct a current, but it did clean off contacts so that
they made a better, lower resistance connection. It made a big difference
on the contacts was was checking.
In any case I suggest that everyone make it a habit to unplug any
appliance that they are going to open up.

I am not sure of the rule, but I believe that some if not all current
three wires plugs for 240 are two legs and a ground. An appliance may not
need 120 or it may use a transformer. You may be able to tell by taking a
good look at where that third conductor goes and if it is connected to the
case.

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